The field of the invention pertains to double doors that close together without a door frame in between. Normally the active door includes handles and a latch to provide for opening and closing the active door. Thus, at the intermediated handle elevation the passive door includes a strike plate and recess for the latch. The passive door may also include a separate strike plate and recess for a dead bolt at the intermediate level.
At the top corner of the passive door directly above the intermediate elevation strike plate is a vertically movable bolt engageable with a strike plate and recess in the door frame. Extended, the vertically movable bolt prevents opening of the passive door unless the active door is first opened releasing the cam actuator for the vertically movable bolt. In certain applications such as fire doors a bimetallic link will be included in the vertical bolt mechanism to prevent opening of the passive door in the event of high temperatures beyond the door.
Whether a steel door or a wooden door a considerable amount of door structure must be removed at the top corner to accommodate the vertical bolt mechanism. As a result this corner may be significantly weakened in routing out or cutting the door structure without damaging the door surfaces.
With a view toward avoiding significant damage to the passive door structure and simplifying installation of the vertical bolt mechanism the following mechanism configuration has been developed.